The alpha2-adrenoreceptors (α2) are G protein-coupled cell membrane receptors widely distributed in humans and they are sub-classified into three subtypes in human; alpha2A, alpha2B and alpha2C (Bylund et al, Mol. Pharmacol., 1992, 42, 1-5). Alpha2 adrenoreceptors have a multiplicity of biological functions and compounds effecting to these receptors are attractive targets on various diseases (Goodman & Gilman's The Pharmacological Basis of Therapeutics, 12th edition, 2011, chapter 12; Brede et al Biol. Cell 2004, 96, 343-348). Indeed, many alpha2 active compounds have been prepared (Gentili et al, Curr. Top Med. Chem., 2007, 7, 163-186) and tested in clinical settings (Crassous et al, Curr. Top Med. Chem., 2007, 7, 187-194). For example, partial alpha2A agonist clonidine is used as a blood-pressure lowering agent and non-alpha2 subtype nonselective full agonist dexmedetomidine is used as a sedative in the intensive care units.
U.S. Pat. No. 3,438,995 discloses some isochroman and isothiochroman derivatives and suggests them to be useful as rubber accelerators, anti-oxidants, corrosion inhibitors, central nervous system (CNS) depressants and anti-inflammatories. WO 2007/085558 discloses a variety of imidazole derivatives useful as TAAR ligands for the treatment of variety of disorders, including various CNS disorders.